The guilty pleas last week by two former Credit Suisse Group (CS) traders, on charges of falsifying their company's asset values, revive an age-old question: How dumb do you have to be to get criminally convicted for a fraud you committed while working at a bank deemed too big to fail?

It's a shame the television series "America's Dumbest Criminals" went off the air more than a decade ago, because the cases of Salmaan Siddiqui, 36, and David Higgs, 42, would have provided wonderful fodder as an example of high finance gone feloniously brain-dead. Sure, their stories might not have the same mainstream appeal as, say, the video of a gun-wielding robber at a convenience store who wore a see-through plastic bag over his head as a disguise.